Process for continuous production of branched polyarylene sulfides

ABSTRACT

A process for continuous production of a branched polyarylene sulfide, which includes pre-polymerizing a sulfur source with a dihalogenated aromatic compound in such a manner that the reaction rate of the dihalogenated aromatic compound is less than 95% so as to produce a polyarylene sulfide, prepolymer, and polymerizing the prepolymer in the presence of a branching agent while dispersing the phase of the polymer into the form of spherical droplets in the phase of a solvent. When the prepolymer is added to the solvent phase to which a phase separator is beforehand added, spherical droplets of the polymer phase can be produced.

TECHNICAL FIELD

The present invention relates to a process for continuous production ofa branched polyarylene sulfide.

RELATED ART

Hitherto, the polymerization of polyarylene sulfide has been carried outin a batch manner. However, in recent years, the request that thepolymerization should be continuously performed has been made high fromthe viewpoint of an improvement in the producing efficiency thereof.Processes for continuous polymerization of a polyarylene sulfide aredisclosed in, e.g., U.S. Pat. Nos. 4,056,515, 4,060,520 and 4,066,632.However, all of polyarylene sulfides obtained by these processes havelow molecular weights.

As a process for making the molecular weight of a polyarylene sulfidehigh, suggested is a continuously-polymerizing process in which a phaseseparator (such as water, sodium acetate or alkali metal salt) is usedto separate two phases of a polymer phase and a solvent phase.

For example, in JP-A-9-169844, in order to increase the molecular weightof a polyarylene sulfide, there is suggested a process in which areaction system is separated into a polymer phase and a solvent phase,the ratio between the polymer phase and the solvent phase is madeconstant to produce the polyarylene sulfide, and then the polymer phaseand the solvent phase are taken out separately. However, in thisprocess, there are such problems that the pipe structure of the devicefor the polymerization is complicated or the flow rate of the reactionsolution is not easily controlled. Thus, this process is insufficientfor coping with the problems. In other words, in continuouspolymerization using a phase separator, it is important that when apolymer phase and a solvent phase are taken out from a polymerizingtank, the ratio between the polymer phase and the solvent phase is keptconstant to keep the polyarylene sulfide composition (concentration) inthe polymerizing tank constant at all times.

Thus, in order to solve such problems, Japanese Patent Application No.2001-068495 suggests a process in which a prepolymer pre-polymerized ina batch reactor is introduced into a polymerizing tank in which a phaseseparator and a solvent are beforehand charged so as to producespherical droplets of a polymer phase, thereby polymerizing apolyarylene sulfide continuously. In other words, the polymerizationadvances into the state that the polymer phase is homogeneouslydispersed into spherical droplets in the solvent phase in thepolymerizing tank. According to this process, the solvent phase and thepolymer phase are together taken out from the polymerizing tank in thestate that they are mixed. At this time, the polymer phase issubstantially homogeneously dispersed as well in the solvent phase;therefore, the solvent phase and the polymer phase can be taken out at aconstant ratio so that the polyarylene sulfide composition(concentration) in the polymerizing tank can be kept constant. As aresult, a linear polyarylene sulfide can be produced in a stable statefor a long time.

However, it has been found out from further repeated investigations thatwhen a branched polyarylene sulfide is produced by this process, thepolymer phase thereof is not easily kept in spherical droplets for along time (for example, 100 hours or more) and the polymer phase/solventphase cannot be taken out at a constant ratio from the polymerizingtank, whereby the sulfide cannot be stably produced for a long term.That is, the polymer phase becomes an indeterminate form to disperseinto the solvent phase so that a mixture of the polymer phase and thesolvent phase cannot be taken out at a constant ratio from thepolymerizing tank. It is probably considered that the reason why thespherical droplets of the polymer phase cannot be maintained is that thephysical property of branched polyarylene sulfide is different from thatof linear polyarylene sulfide.

In light of the above-mentioned problems, the present invention has beenmade. An object thereof is to provide a process for continuousproduction of a branched polyarylene sulfide which makes it possible toform spherical droplets of a polymer layer over a long time and producethe branched polyarylene sulfide stably.

The present inventors have repeated eager researches for attaining theabove-mentioned object, so as to find out that when the reaction rate ofa prepolymer is set to less than 95% in pre-polymerization, a branchedpolyarylene sulfide can be continuously polymerized in the state thatspherical droplets are formed for a long time. Thus, the presentinvention has been made.

DISCLOSURE OF THE INVENTION

According to a first aspect of the present invention, there is provideda process for continuous production of a branched polyarylene sulfide,which comprises pre-polymerizing a sulfur source with a dihalogenatedaromatic compound in such a manner that the reaction rate of thedihalogenated aromatic compound is less than 95% to produce apolyarylene sulfide prepolymer, and polymerizing the prepolymer in thepresence of a branching agent while dispersing the phase of the polymerinto the form of spherical droplets in the phase of a solvent.

According to a second aspect of the present invention, there is provideda process for continuous production of a branched polyarylene sulfide,which comprises pre-polymerizing a sulfur source with a dihalogenatedaromatic compound in the presence of a branching agent in such a mannerthat the reaction rate of the dihalogenated aromatic compound is lessthan 95% to produce a polyarylene sulfide prepolymer, and polymerizingthe prepolymer while dispersing the phase of the polymer into the formof spherical droplets in the phase of a solvent.

In the first and second aspects, in both the pre-polymerization step andthe polymerization steps, the reaction can be carried out in thepresence of a branching agent.

BEST MODE FOR CARRYING OUT THE INVENTION

A process for continuous production of a branched polyarylene sulfide isdescribed hereinafter.

The production process of the present invention comprises reacting asulfur source with a dihalogenated aromatic compound in such a mannerthat the reaction rate of the dihalogenated aromatic compound is lessthan 95%, so as to produce a polyarylene sulfide prepolymer (apre-polymerization step), and polymerizing the prepolymer whiledispersing the phase of the polymer into the form of spherical dropletsin the phase of a solvent (a regular polymerization step).

First, the pre-polymerization step is described.

In this step, a sulfur source is caused to react with a dihalogenatedaromatic compound in such a manner that the reaction rate of thedihalogenated aromatic compound is less than 95%, preferably from 30 to90%, more preferably 40 to 80%, so as to produce a polyarylene sulfideprepolymer. If the reaction rate of the dihalogenated aromatic compoundis 95% or more, spherical droplets of a polymer phase are not generatedfor a long term in the regular polymerization step, which will bedescribed later. It appears that this is because the surface tension ofthe droplets of the polymer changes. On the other hand, if the reactionrate is less than 30%, the reaction rate is not sufficiently raised inthe regular polymerization step so that the molecular weight of theresultant polyarylene sulfide may not be made high.

The reaction rate of the dihalogenated aromatic compound can becalculated from the mol ratios before and after the reaction.

The pre-polymerization step is preferably performed in an aproticorganic solvent. Examples thereof include amide compounds such asN,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetoamide,N,N-diethylacetoamide, N,N-dipropylacetoamide, and N,N-dimethylbenzoicamide; N-alkylcaprolactams such as caprolactam, N-methylcaprolactam,N-ethylcaprolactam, N-ispropylcaprolactam, N-isobutylcaprolactam,N-n-propylcaprolactam, N-n-butylcaprolactam, andN-cyclohexylcaprolactam; lactam compounds such as N-methyl-2-pyrrolidone(NMP), N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone,N-isobutyl-2-pyrrolidone, N-n-propyl-2-pyrrolidone,N-n-butyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-methyl-3-methyl2-pyrrolidone, N-ethyl-3-methyl-2-pyrrolidone,N-methyl-3,4,5-trimethyl-2-pyrrolidone, N-methyl-2-piperidone,N-ethyl-2-piperidone, N-isopropyl-2-piperidone,N-methyl-6-methyl-2-piperidone, and N-methyl-3-ethyl-2-piperidone; ureacompounds such as tetramethylurea, N,N′-dimethylethyleneurea, andN,N′-dimethylpropyleneurea; sulfur compounds such as dimethylsulfoxide,diethylsulfoxide, diphenylsulfone, 1-methyl-1-oxosulfolane,1-ethyl-1-oxosulfolane, and 1-phenyl-1-oxosulfolane; and cyclic organicphosphorus compounds such as 1-methyl-1-oxophospholan,1-n-propyl-1-oxophospholan, and 1-phenyl-1-oxophospholan. Of these,N-alkylcaprolactams and N-alkylpyrrolidones are preferable, andN-methyl-2-pyrrolidone is particularly preferable.

These aprotic organic solvents may be used alone or in the form of amixture of two or more thereof. The solvents may be mixed with adifferent solvent component which does not hinder the object of thepresent invention, such as water, and the mixed solvent can be used asan aprotic organic solvent.

Examples of the sulfur source include alkali metal sulfides, alkalimetal hydrosulfides, and hydrogen sulfide. Of these, preferable arealkali metal sulfides, and more preferable is lithium sulfide.

In order to make the reaction efficiency high in the present invention,the sulfur source can be used together with an alkali metal hydroxidesuch as lithium hydroxide.

Examples of the dihalogenated aromatic compound include dichlorobenzenessuch as m-dichlorobenzene, and p-dichlorobenzene; alkyl-substituteddichlorobenzene or cycloalkyl-substituted dichlorobenezene such as2,3-dichlorotoluene, 2,5-dichlorotoluene, 2,6-dichlorotoluene,3,4-dichlorotoluene, 2,5-dichloroxylene, 1-ethyl-2,5-dichlorobenzene,1,2,4,5-tetramethyl-3,6-dichlorobenzene, 1-n-hexyl-2,5-dichlorobenzene,and 1-cyclohexyl-2,5-dichlorobenzene; aryl-substituted dichlorobenzenessuch as 1-phenyl-2,5-dichlorobenzene, 1-benzyl-2,5-dichlorobenzene, and1-p-toluyl-2,5-dichlorobenzene; dichlorobiphenyls such as4,4′-dichlorobiphenyl; and dichloronaphthalenes such as1,4-dichloronaphthalene, 1,6-dichloronaphthalene, and2,6-dichloronaphthalene. Of these, dichlorobenzens are preferable, andp-chlorobenzene is particularly preferable.

As the dihalogenated aromatic compound, compounds wherein the chlorinesof the above-mentioned dichloro aromatic compounds are substituted withfluorines, bromines and iodines can be similarly used.

In the pre-polymerization step, the sulfur source and the dihalogenatedaromatic compound are caused to react with each other preferably from180 to 220° C., more preferably from 190 to 210° C. If the reaction timeis lower than 180° C., a long time may be required to advance thereaction. On the other hand, if it is over 230° C., a polymer phase insubsequent continuous polymerization may not become spherical dropletsover a long time. It appears that this is because physical properties ofthe polymer droplets, such as the surface tension thereof, change.

The concentration of the sulfur source in the aprotic organic solvent ispreferably set into the range of 1.4 to 2.8 mol/L, more preferably from1.7 to 2.3 mol/L. If the concentration is out of the range, sphericaldroplets of the polymer phase may not be generated.

The mol ratio between the dihalogenated aromatic compound and sulfuratoms in the sulfur source (the dihalogenated aromatic compound/thesulfur) is preferably from 0.90 to 1.10, more preferably from 0.95 to1.00. If the mol ratio is smaller than 0.90, the polyarylene sulfide maydecompose during the reaction. On the other hand, if the ratio is largerthan 1.10, costs for subsequent collection of the starting materials maybecome high.

The mol ratio between water mixed with the aprotic organic solvent andthe sulfur atoms in the sulfur source (water/the sulfur) is preferablyfrom 0.20 to 2.00, more preferably from 0.30 to 1.50. If the mol ratiois smaller than 0.20, the reaction system may decompose in subsequentcontinuous polymerization. On the other hand, if the ratio is largerthan 2.00, the reaction rate in the subsequent continuous polymerizationmay lower so that the polymer yield become low.

In the pre-polymerization step, the manner for polymerizing theprepolymer is not particularly limited if the reaction rate of thedihalogenated aromatic compound can be set to less than 95%. Thepolymerizing manner may be, for example, a batch manner or a continuousmanner. The batch manner is preferably used.

The branching agent may be introduced in the pre-polymerization step soas to pre-polymerize the prepolymer in the presence of the branchingagent, or may be introduced in the regular polymerization step whichwill be described later, so as to polymerize a polymer in the presenceof the branching agent.

The following describes the regular polymerization step.

In this step, the prepolymer obtained in the pre-polymerization step ispolymerized to produce a polymer. At this time, the polymerization isperformed in the state that spherical droplets of the phase of thepolymer are dispersed in the phase of a solvent.

Herein, the word “spherical” includes meanings of complete spheres,elliptic spheres, products that have a shape similar thereto, orproducts that have a shape of a deformed sphere but substantially closeto a sphere. The size thereof is usually 1000 microns or less when thepolymerization ends.

Examples of the method for forming the spherical droplets include amethod in which the prepolymer is added to the phase of a solvent towhich a phase separator is beforehand added, and a method in whichspherical droplets are formed beforehand by batch polymerization underspecific conditions, and then the prepolymer is added thereto.

In the former method, the pre-polymerized prepolymer (usually at 180 to220° C.) is put into a reactor (usually at 230 to 280° C.), for theregular polymerization, which contains a phase separator, therebyforming the spherical droplets. Specifically, when NMP is used as thesolvent in the reactor for the pre-polymerization, the prepolymer isdispersed in the form of fine particles not dissolved in NMP. When thisprepolymer is put into the reactor for the regular polymerization whichcontains lithium chloride (phase separator) and NMP, the polymer isdissolved since the temperature of the reactor is high. Consequently,spherical droplets composed of the polymer and the solvent are formed.The spherical droplets are substantially homogeneously dispersed in thesolvent phase. In this state, the prepolymer is polymerized to produce apolymer.

In the latter method, the temperature of a reactor for the regularpolymerization, in which a monomer is put, is raised up to thetemperature for the polymerization thereof in a short time. As a result,spherical droplets composed of a polymer and the solvent are formed. Forexample, the temperature is raised from room temperature to about 260°C. in about 30 minutes. In the state that the spherical droplets areformed in this way, a prepolymer which is separately pre-polymerized isput in the reactor for the regular polymerization and then thepre-polymer is polymerized.

In order to form the spherical droplets in any one of theabove-mentioned methods, a phase separator having a given concentrationis contained in the reactor for the regular polymer. The concentrationof the phase separator is preferably from 2.8 to 5.6 mol/L, morepreferably from 3.4 to 4.6 mol/L per liter of the solvent. If theconcentration is less than 2.8 mol/L, the spherical droplets of thepolymer phase may not be generated. On the other hand, if theconcentration is more than 5.6 mol/L, costs for a subsequent process forcollecting the starting mateirals may become high.

Examples of the phase separator include alkali metal salts such aslithium chloride, sodium acetate and lithium, and water. Of these,lithium chloride is preferable.

In the case that a polyarylene sulfide is produced from thedichloroaromatic compound and lithium sulfide, lithium chloride isgenerated as a by-product. This functions as a phase separator.

In the regular polymerization step, the polymerization reaction of theprepolymer advances in the state that the spherical droplets aredispersed for a long term. As a result, a branched polyarylene sulfidehaving a high molecular weight is continuously produced.

In this step, the prepolymer produced in the pre-polymerization step maybe caused to react alone as a polymerization starting material. It isallowable to add the above-mentioned sulfur source, dihalogenatedaromatic compound and so on to the prepolymer, adjust the mol ratiotherebetween, and cause these to react with each other as polymerizationstarting materials.

As described above, the branching agent may be put in thepre-polymerization step, or may be put in the regular polymerizationstep.

Examples of the branching agent include halogenated aromatic compoundseach having active hydrogen, and polyhalogenated aromatic compounds andpolyhalogenated aromatic nitro compounds each having in a singlemolecule thereof three or more halogen atoms. Of these, preferable isthe polyhalogenated aromatic compounds, and more preferably is1,2,4-trichlorobenzene (TCB).

Usually, the mol ratio of the branching agent to sulfur atoms in thesulfur source (the branching agent/S) is from about 0.001 to about 0.05.If the mol ratio is too small, a polymer wherein the characteristic ofbranch is not exhibited may be obtained. On the other hand, if the molratio is too large, the molecular weight of the polymer may become toohigh so that the polymer be gelatinized. As a result, the reaction maynot be able to be controlled.

In this step, the mol ratio of Li to the sulfur source (Li/S) ispreferably from 2.00 to 2.40, more preferably from 2.05 to 2.30. If themol ratio is smaller than 2.00, a polymer having a sufficient molecularweight may not be obtained. On the other hand, if the mol ratio is morethan 2.40, costs may be demanded for collecting Li.

The mol ratio of the dihalogenated aromatic compound to the sulfursource (the dihalogenated aromatic compound/sulfur) is preferably from0.95 to 1.20, more preferably from 1.00 to 1.10. If the mol ratio isless than 0.95, the polyarylene sulfide may decompose. On the otherhand, if the mol ratio is more than 1.20, costs may be demanded forcollecting the dihalogenated aromatic compound unreacted.

The dihalogenated aromatic compound/the solvent (polymerizationconcentration) is preferably from 1.4 to 2.8 mol/L, more preferably form1.7 to 2.3 mol/L. If the concentration is less than 1.4, theproductivity of the polymer may deteriorate. On the other hand, if theconcentration is more than 2.8, a polymer having a sufficient molecularweight may not be obtained.

In the regular polymerization step, the prepolymer is polymerizedpreferably at 230 to 280° C., more preferably at 245 to 275° C., evenmore preferably at 250 to 270° C. If this temperature is lower than 230°C., a polymer having a sufficient molecular weight may not be obtained.On the other hand, if the temperature is higher than 280° C., thepolyarylene sulfide may decompose.

In the regular polymerization step, the average residence time of thepolymerization starting material(s) in the polymerizing tank ispreferably from 0.5 to 10 hours, more preferably from 1 to 7 hours, evenmore preferably from 2 to 5 hours. If this time is shorter than 0.5hour, a polymer having a sufficient molecular weight may not beobtained. On the other hand, if the time is longer than 10 hours, theproduction efficiency may deteriorate or the polymer may be gelatinized.

In the regular polymerization step, the number of the used polymerizingtank(s) (stage(s)) is not particularly limited, and many tanks (stages)may be used. The temperature condition may be changed to two or morestage conditions. In this case, it is sufficient that the polymer phasein at least one of the polymerizing tanks is in a spherical dropletstate and the process of the present invention can be applied in thetank. Preferably, the process of the present invention is applied to atleast the last of the polymerizing tanks. However, the process can beapplied to all the polymerizing tanks.

The polymerizing tank is not limited to any especial kind. Preferably, areaction tank suitable for a completely mixing tank is used. Thepolymerizing tank has stirring fans. The stirring fans are preferablylarge-sized stirring fans the tips of which have no notches, anchorfans, screw fans, Max Blend fans, large-sized paddle fans, or full-zonefans.

In the present invention, the specific prepolymer produced in thepre-polymerization step is used to produce a branched polyarylenesulfide; therefore, in the regular polymerization step, the form of thepolymer phase containing the continuously-produced branched polyarylenesulfide can be kept in the form of spherical droplets for a long time,for example, 100 hours or more.

This makes it possible that when a mixture of the polymer phase and thesolvent phase is continuously taken out from the polymerizing tank, thepolymer phase and the solvent phase are taken out at a constant ratiofor a long time. As a result, the concentration of the branchedpolyarylene sulfide in the polymerizing tank can be kept constant.Accordingly, the branched polyarylene sulfide can be stably obtained.

If necessary, the polymer phase and the solvent phase taken out at aconstant ratio may be transferred to a next polymerizing tank so as torepeat the regular polymerization step again.

About conditions and so on other than the above-mentioned those in theregular polymerization step, for example, conditions and so on inJP-A-6-248077 can be used.

Water can be added to the polymerization solution after the regularpolymerization step to such an extent that the branched polyarylenesulfide is not solidified, thereby performing washing operation. Theamount of the water is varied dependently on the amount of thepolymerization solution or the temperature thereof. It is sufficientthat the water amount is such an amount that does not cause thesolidification or precipitation of the branched polyarylene sulfide byexcessive cooling of the sulfide. In general, it is preferable that inthe washing tank, the polymerization solution and the water are stirredto be sufficiently mixed with each other.

The washing solution is not limited to any especial kind if impuritiesor by-products attached to the polymer are dissolved in the solution andthe solution produces no bad effect on the polymer. Examples thereofinclude methanol, acetone, benzene, toluene, water and NMP. Of these,water is preferable.

Separating operation in a separating tank is applied to thepolymerization solution after the polymerization reaction ends in orderto separate the solution into the phase of the polymer and the phase ofthe solvent.

As a method for preparing lithium sulfide via lithium hydroxide from theseparated solvent phase (made mainly of NMP, water and lithiumchloride), for example, a method described in JP-A-2000-319009 can beused.

In order to obtain more satisfactory washing and separating effects, thewashing and separating steps may be repeated any plural times.

In the present invention, the polymer phase subjected to the washing andseparating steps contains the solvent still. Thus, it is preferable toremove the solvent. The operation for the solvent removal is not limitedto any especial kind, and may be according to a solvent-removing methodused in a known process for producing a polyarylene sulfide (forexample, a flash method disclosed in JP-A-7-033878).

The branched polyarylene sulfide subjected to the solvent-removingoperation can be taken out in a melted state, or cooled and solidifiedin an appropriate manner in a granular form. The method for the coolingmay be cooling with air, water, oil or the like.

In the case that various products are formed from the branchedpolyarylene sulfide obtained by the present invention, the following maybe appropriately incorporated into the branched polyarylene sulfide ifnecessary: a different polymer, a pigment, graphite, metal powder, glasspowder, quartz powder, talc, calcium carbonate, glass fiber, carbonfiber, fillers such as various whiskers, a stabilizer, and a releasingagent.

The branched polyarylene sulfide obtained by the present invention canbe used suitably for the material of various molded products, forexample, the material of films, fibers, mechanical parts, electricparts, electronic parts, and others.

EXAMPLES

The present invention is more specifically described by way of workingexamples hereinafter. The solution viscosity of a polymer was measuredwith the following method.

Solution viscosity (ηinh): The viscosity was measured at 206° C. with anUbellohde's viscometer after keeping a sample in an α-chloronaphthalenesolution of 4 g/L concentration and 235° C. temperature for 30 min. todissolve the sample therein. [η] (dL/g)=ln (relative viscosity)/polymerconcentration

Example 1

(1) Pre-polymerization (Batch Reaction)

Into a 10-L autoclave equipped with a stirrer having stirring fans werecharged 3.5 L of N-methyl-2-pyrrolidone (NMP), 47.9 (2 mol) of anhydrouslithium hydroxide, and 459.5 g (10 mol) of lithium sulfide, and then thetemperature thereof was raised to 210° C. in the atmosphere of nitrogenwhile the mixture was stirred. When the temperature reached 210° C., amixture of 0.83 L of NMP, 1,426 g (9.7 mol) of p-dichlorobenzene (pDCB)and 54.2 g (3 mol) of water was added into the autoclave. The componentstherein were caused to react at 210° C. for 2 hours to synthesize apolyarylene sulfide oligomer (prepolymer). The reaction rate of pDCB inthe pre-polymerization was 75%.

In the pre-polymerization, the sulfur concentration was 2.24 (mol/L),and the mol ratio between the chemicals was as follows: Li/S=2.20,pDCB/S=0.97, and H₂O/S=0.30.

The prepolymer was synthesized in accordance with an amount necessaryfor continuous polymerization in the next step, and provided forreaction.

(2) Regular Polymerization (Continuous Reaction)

Into an autoclave equipped with a stirrer having full-zone fans werecharged 730 g of lithium chloride, 4.9 L of NMP, and 233 g of water, andthen the temperature thereof was raised to 260° C. Next, into 1 kg ofthe prepolymer synthesized in the above (1) were incorporated 16.0 g ofpDCB, 218.6 g of NMP, 2.82 g of 1,2,4-trichlorobenzene (TCB) and 33.6 gof water so as to adjust the mol ratio between the starting materials.While the prepared prepolymer was kept at 60° C., a gear pump was usedto introduce the prepolymer continuously at a rate of 50.0 g/min. into apolymerizing tank to conduct continuous polymerization for a polyarylenesulfide. At this time, in the polymer phase dispersed in the solventphase containing NMP, spherical droplets were generated.

In the regular polymerization, the concentration of lithium chloridecharged before the reaction was 3.52 (mol/L), and the mol ratio betweenthe chemicals after the adjustment, that is, the mol ratio at the timeof the regular polymerization was as follows: pDCB/S=1.04, Li/S=2.20,H₂O/S=1.50, and TCB/S=0.01. The sulfur concentration was 1.76(mol/NMP-L). The polymerization temperature was set to 260° C. and theaverage residence time (τ) of the polymer in the polymerizing tank wasset to 2 hours.

In order to keep the level of the liquid surface in the polymerizingtank constant, about 250 g of the polymer mixture was withdrawn from awithdrawing nozzle of the polymerizing tank one time every five minutes.This operation was continued for 100 hours. At this time, the state thatdroplets of the polymer phase were dispersed in each sample withdrawnafter 50 hours and 100 hours was evaluated with the eye through amicroscope. The results are shown in Table 1. The standard for theevaluation was as follows.

◯: The polymer phase was dispersed in a spherical droplet state.

X: The polymer phase was dispersed in an indeterminate form state.

The sample withdrawn after 100 hours was subjected toinclination-filtration so as to be separated into the polymer and thepolymerization solution. The resultant polymer was heated and stirredwith hot water 2 times for washing. Thereafter, the polymer wasvacuum-dried at 120° C. for 12 hours. The solution viscosity ηinh ofthis polymer was measured by the above-mentioned method. As a result,the viscosity was 0.24 dL/g. The form of this polymer was spherical.Thereafter, the polymerizing tank was cooled and opened to observe theform of the polymer. As a result, the form was spherical still.

Example 2

Continuous polymerization for a polyarylene sulfide was conducted andthe state that droplets of the polymer phase thereof were dispersed wasevaluated in the same way as in Example 1 except that thepre-polymerization was conducted for 1 hour and the reaction rate ofpDCB was lowered to 50% in Example 1. As a result, in each of sampleswithdrawn after 50 hours and 100 hours, the form of the droplets of thepolymer phase was kept spherical. The polymer after the polymerizingtank was cooled and opened was also kept in a spherical dispersionstate. The solution viscosity ηinh of the polymer was 0.22 dL/g.

Example 3

Continuous polymerization for a polyarylene sulfide was conducted andthe state that droplets of the polymer phase thereof were dispersed wasevaluated in the same way as in Example 1 except that thepre-polymerization was conducted for 0.5 hour and the reaction rate ofpDCB was lowered to 40% in Example 1. As a result, in each of sampleswithdrawn after 50 hours and 100 hours, the form of the droplets of thepolymer phase was kept spherical. The polymer after the polymerizingtank was cooled and opened was also kept in a spherical dispersionstate. The solution viscosity ηinh of the polymer was 0.20 dL/g.

Example 4

Continuous polymerization for a polyarylene sulfide was conducted andthe state that droplets of the polymer phase thereof were dispersed wasevaluated in the same way as in Example 1 except that the chargingamount of TCD was changed to 1.41 g and the charging timing thereof waschanged to the same time when pDCB was charged in the pre-polymerizationinstead of the time of the regular polymerization in Example 1. As aresult, in each of samples withdrawn after 50 hours and 100 hours, theform of the droplets of the polymer phase was kept spherical. Thepolymer after the polymerizing tank was cooled and opened was also keptin a spherical dispersion state. The solution viscosity ηinh of thepolymer was 0.23 dL/g.

Comparative Example 1

Continuous polymerization for a polyarylene sulfide was conducted andthe state that droplets of the polymer phase thereof were dispersed wasevaluated in the same way as in Example 1 except that thepre-polymerization was conducted for 5 hours and the reaction rate ofPDCB was raised to 95% in Example 1. As a result, the form of dropletsof the polymer phase in a sample withdrawn after 50 hours was keptspherical. However, the form of droplets of the polymer phase in asample withdrawn after 100 hours was not kept spherical, and was anindeterminate form. The polymer after the polymerizing tank was cooledand opened was in an indeterminate granular form. The solution viscosityηinh of the polymer was 0.27 dL/g. TABLE 1 Comparative Items UnitExample 1 Example 2 Example 3 Example 4 Example 1 Pre-polymerizationSulfur mol/L 2.24 2.24 2.24 2.24 2.24 concentration Li/S mol/mol 2.202.20 2.20 2.20 2.20 PDCB/S mol/mol 0.97 0.97 0.97 0.97 0.97 H₂O/Smol/mol 0.30 0.30 0.30 0.30 0.30 Reaction ° C. 210 210 210 210 210temperature Reaction rate % 75 50 40 75 95 of pDCB Regularpolymerization Li/Cl/NMP mol/L 3.52 3.52 3.52 3.52 3.52 Sulfur mol/L1.76 1.76 1.76 1.76 1.76 concentration Li/S mol/mol 2.20 2.20 2.20 2.202.20 PDCB/S mol/mol 1.04 1.04 1.04 1.04 1.04 H₂O/S mol/mol 1.50 1.501.50 1.50 1.50 TCB/S mol/mol 0.01 0.01 0.01 0.005 0.01 Reaction ° C. 260260 260 260 260 temperature τ hr 2.0 2.0 2.0 2.0 2.0 Dispersion StateAfter 50 hours ∘ ∘ ∘ ∘ ∘ After 100 hours ∘ ∘ ∘ ∘ x Solution viscosityηinh (dL/g) 0.24 0.22 0.20 0.23 0.27

Industrial Applicability

According to the present invention, it is possible to provide a processfor continuous production of a branched polyarylene sulfide in whichspherical droplets of the layer of the polymer can be formed for a longtime and the branched polyarylene sulfide can be produced stably.

1. A process for continuous production of a branched polyarylenesulfide, which comprises: pre-polymerizing a sulfur source with adihalogenated aromatic compound in such a manner that the reaction rateof the dihalogenated aromatic compound is less than 95% to produce apolyarylene sulfide prepolymer, and polymerizing the prepolymer in thepresence of a branching agent while dispersing a phase of the polymerinto the form of spherical droplets in a phase of a solvent.
 2. Aprocess for continuous production of a branched polyarylene sulfide,which comprises: pre-polymerizing a sulfur source with a dihalogenatedaromatic compound in the presence of a branching agent in such a mannerthat the reaction rate of the dihalogenated aromatic compound is lessthan 95% to produce a polyarylene sulfide prepolymer, and polymerizingthe prepolymer while dispersing a phase of the polymer into the form ofspherical droplets in a phase of a solvent.
 3. The process forcontinuous production of a branched polyarylene sulfide according toclaim 1, wherein the prepolymer is produced in a batch manner.
 4. Theprocess for continuous production of a branched polyarylene sulfideaccording to claim 1, wherein the pre-polymerizing is performed at 180to 220° C.
 5. The process for continuous production of a branchedpolyarylene sulfide according to claim 1, wherein the polymerizing isperformed at 230 to 280° C.